Spatial Variation of Heavy Metals Uptake in Ashar Plant (<i>Calotropis procera</i>) Organs: Implications for Air Pollution Mitigation in Riyadh

Phytoremediation is an eco-friendly and effective method that uses plants to reduce heavy metal pollution by absorbing and accumulating contaminants from the environment. This research focused on the native Al-Ashar plant and examined its potential as a bioindicator and agent for cleaning heavy metal contamination near a cement factory in Riyadh, Saudi Arabia. Soil and plant samples were gathered from sites at different distances from the factory (5 m, 50 m, 100 m), including a control site, and analyzed for metals such as copper, iron, manganese, chromium, cobalt, lead, and nickel. The results showed elevated levels of these metals in soil close to the factory, with copper concentrations dropping from 5.04 mg/kg at 5 m to 2.06 mg/kg in the control site. Iron levels were notably higher near the source (5362 mg/kg) compared to the control (2370 mg/kg). Surface soils had consistently greater metal concentrations than deeper layers, suggesting contamination primarily via atmospheric deposition and limited downward movement. In plant tissues, roots contained the highest metal levels, followed by stems and leaves, reflecting differences in metal uptake and transport within the plant. Metal concentrations in plants diminished with increasing distance from the pollution source. Overall, these findings highlight the significant impact of industrial emissions on the spread of heavy metals in urban soils and support the use of Al-Ashar as an effective bioindicator and a candidate for phytoremediation. The study emphasizes the need for integrated soil and vegetation monitoring programs to accurately assess pollution and develop targeted cleanup strategies in industrially affected areas.